Magnetocaloric device

ABSTRACT

The invention relates to a magnetocaloric device, comprising a field generator, arranged to provide a changing external magnetic field and a magnetocaloric regenerator arrangement. The magnetocaloric regenerator arrangement comprises a magnetocaloric element, wherein the magnetocaloric element comprises magnetocaloric material, and wherein the magnetocaloric regenerator arrangement is arranged to be exposed to the changing external magnetic field of the field generator. Furthermore, the invention is characterized in that the magnetocaloric device further comprises an insulating means wherein the insulating means is arranged such that the magnetocaloric regenerator arrangement is hermetically surrounded by the insulating means.

The invention relates to a magnetocaloric device, in particular to amagnetocaloric heat pump, according to the preamble part of claim 1.

Magnetocaloric materials can be used for pumping heat since they changetheir temperature upon an application and removal of an externalmagnetic field.

The magnetocaloric effect occurs under application of an externalmagnetic field to a suitable magnetocaloric material and under anambient temperature in the vicinity of its Curie temperature. Theapplied external magnetic field causes an alignment of the randomlyaligned magnetic moments of the magnetocaloric material from adisordered paramagnetic phase to an ordered ferromagnetic phase and thusa magnetic phase transition, which can also be described as an inducedincrease of the Curie temperature of the material above the ambienttemperature. This magnetic phase transition implies a decrease inmagnetic entropy ΔS_(mag) and in a nearly adiabatic process (thermalisolation from the ambient temperature) leads to an increase in theentropy contribution of the crystal lattice of the magnetocaloricmaterial by phonon generation in order to conserve entropy under theadiabatic condition. As a result of applying the external magneticfield, therefore, a temperature rise (ΔT) of the magnetocaloric materialoccurs.

In technical cooling applications, this additional heat is removed fromthe material by heat transfer to an ambient heat sink. The heat istransported from the material to the ambient heat sink by a heattransfer medium. Water is an example of a heat transfer medium used forheat removal from the magnetocaloric material. For temperatures below 0°C., an antifreeze additive such as ethylene or propylene glycol,ethanol, or a salt may be added to the water.

Subsequently, removing the external magnetic field can be described as adecrease of the Curie temperature back below an initial temperature ofthe magnetocaloric material, and thus allows the magnetic momentsreverting back to a random arrangement. The external magnetic field isremoved under nearly adiabatic conditions, i.e., thermal isolation fromthe ambient temperature, which means that the overall entropy within thesystem stays unchanged. Since the magnetic entropy increases to itsstarting level without the external magnetic field, the entropycontribution of the crystal lattice of the magnetocaloric materialitself is reduced, and under nearly adiabatic process conditions, thus,results in a cooling of the magnetocaloric material below the initialtemperature.

The described process cycle including magnetization and demagnetizationis typically performed periodically in device applications.

Document US 2012/0031107 A1 describes a thermal generator with at leastone thermal module comprising at least two magnetocaloric elements. Thethermal generator is characterized in that it comprises at least twomagnetic assemblies in which one magnetic assembly subjects at least onemagnetocaloric element of the thermal module to alternate magneticphases. The thermal generator is further characterized in that itcomprises a thermally insulating body insulating the magnetic assembliesfrom each other and forming thermally insulated cells comprising onemagnetic assembly and its corresponding magnetocaloric elements.

The prior art designs can be improved. The object of the invention is tocreate an improved magnetocaloric device. In particular it is an objectof the invention to reduce heat leaks caused by the temperaturedifferences between the environment of the magnetocaloric material andthe magnetocaloric material itself.

The object is achieved according to the invention with a magnetocaloricdevice as defined in claim 1.

The invention provides a magnetocaloric device, in particular to amagnetocaloric heat pump, comprising:

a field generator, preferably formed by a magnet assembly, arranged toprovide a changing external magnetic field, preferably a periodicallychanging external magnetic field,

a magnetocaloric regenerator arrangement, comprising a magnetocaloricelement, preferably a plurality of magnetocaloric elements, wherein themagnetocaloric element comprises magnetocaloric material, and whereinthe magnetocaloric regenerator arrangement is arranged to be exposed tothe changing external magnetic field of the field generator.

According to the invention the magnetocaloric device further comprises:

an insulating means, wherein the insulating means is arranged such thatthe magnetocaloric regenerator arrangement is hermetically surrounded bythe insulating means.

The magnetocaloric device according to the invention advantageouslyprovides an insulating means around the magnetocaloric element, whichcomprises the magnetocaloric material. In particular, the thermalconductivity between the magnetocaloric element and the magnet assemblyand/or the ambient environment is reduced compared to magnetocaloricdevices without an insulation means that surrounds the magnetocaloricelement.

By providing a reduced thermal conductivity, the magnetocaloric deviceaccording to the invention enables a reduced amount of heat leaks andtherefore more heat can be pumped for a given work input, which resultsin an improved efficiency of the magnetocaloric device. Besides the lowthermal conductivity, a low heat transfer of parts of the magnetocaloricdevice can advantageously reduce the overall heat transfer coefficientof the magnetocaloric device. In particular, the insulating means canprevent or decrease water condensation, freezing or heat transfer to theambient or between components in the system at different temperatures,which are thermally connected by the ambient environment. The heattransfer coefficient for natural convection is typically less than 10W/m²/K. In contrast, the heat transfer due to condensation typicallyleads to a heat transfer coefficient larger than 100000 W/m²/K, and theconvection forced by a rotating field generator can lead to a heattransfer coefficient of more than 100 W/m²/K. Therefore it isparticularly advantageous to provide a magnetocaloric device, whereinthe insulating means can reduce the heat transfer due to condensationand/or the convection forced by a rotating field generator.

The highest temperature gradients of the magnetocaloric device areusually in a surrounding of the magnetocaloric element, according to aheating and cooling of the magnetocaloric material during themagnetization and demagnetization phases triggered by the periodicallychanging external magnetic field. Therefore it is particularlyadvantageous to provide the insulating means in the surrounding of themagnetocaloric element.

A further advantage of the insulating means is that the magnetocaloricregenerator arrangement is protected against influences of theenvironment, such as water, dust or dirt. This is particularlyadvantageous for allowing an outdoor use of the magnetocaloric device orfor using the magnetocaloric device in rooms with a high humidity.

The magnetocaloric device according to the invention can be amagnetocaloric heat pump that is arranged to be used as a cooling deviceor as a heating device. More particularly, the magnetocaloric device canbe a wine cooler, a refrigerator, a freezer or an air-conditioner.

In the following, developments of the magnetocaloric device according toclaim 1 of the invention will be described.

In a preferred development the magnetocaloric device further comprises afluid directing system, comprising at least a first and a secondchannel, arranged to direct a fluid through the first channel to themagnetocaloric regenerator arrangement and to direct the fluid throughthe second channel away from the magnetocaloric regenerator arrangement,and wherein the insulating means further comprise a flow-through for apassing of the fluid through the at least first and second channel. Theat least first and second channels are typically arranged for providinga fluid flow of the fluid directing system through the flow-through to aheat exchanger outside of the insulating means. In order to not disturba heat exchange of the heat exchanger by the insulating means, anarranging of the heat exchanger outside of the insulating means isparticularly advantageous.

In a preferred development, the insulating means is an insulatingcasing. The insulating casing of a preferred variant is at least partlynot in contact with the magnetocaloric regenerator arrangement.Furthermore, the insulating casing is filled or adapted to be filledwith an insulation. The insulator casing might be an enclosure or ashield and it can be made of different materials, such as for instanceglass, a metal or plastic. It can also be provided as a foam, filledwith air or a further fluid as insulation. It is advantageous to providean insulating casing since this casing can be easily arranged such thatthe magnetocaloric regenerator arrangement is hermetically surrounded bythe insulating casing. The magnetocaloric device according to theinvention can therefore lead to cheap and simple additional productionsteps compared to prior art magnetocaloric devices.

In a preferred variant of the previous development, the insulation has alower thermal conductivity than atmospheric air. This is particularlyadvantageous for providing a thermal insulation of the magnetocaloricregenerator arrangement. In another variant, the insulation has a higherthermal conductivity, as it is the case for an example for an insulationcasing that is filled with a foam.

In an alternative development, the insulating means is an insulatingcoating, which is completely in contact with the magnetocaloricregenerator arrangement. The insulating coating might be for instance afoam, a varnish, a paint or a foil. The insulating coating canadvantageously protect the magnetocaloric element against influences ofthe environment, such as rain, dust or dirt. It is particularly simpleto provide an insulating coating that hermetically surrounds themagnetocaloric arrangement by automated production steps.

In a preferred development of the magnetocaloric device the flow-troughis arranged to leave a gap between insulating casing and the at leastfirst and second channel and a sealing member is arranged to seal thegap. In a variant of this development, the at least first and secondchannel are configured to be rotated with respect to the casing and thesealing member is formed as a rotational seal or as a sealing bearingallowing a rotation of the at least first and second channel whilesealing the gap to the insulating casing. This can be particularlyadvantageous for the magnetocaloric device, wherein the first and thesecond channel are integrated into a crankshaft that rotates the fieldgenerator with respect to the magnetocaloric regenerator arrangement.

Futhermore, the sealing member may be chosen in order to thermallydisconnect the component from the insulating casing. In a variant ofthis development, this is realized by using a material with low thermalconductivity compared to the materials that the insulating materials andthe shaft are made from. This can be ceramic materials, polymericmaterials, metals or metal alloys with comparatively low thermalconductivity, or a combination thereof. Furthermore, the shape can besuch that advantageously little cross section exists for thermalconduction from the component to the insulating casing, or a porous orhollow structure can decrease the thermal connection between the atleast first and second channel and the insulating casing.

In a further preferred development, the magnetocaloric device furthercomprises a filling valve arranged at the insulating casing andconfigured to allow a filling of the insulating casing with theinsulation. The filling valve can provide a comfortable way for thefilling of the magnetocaloric device with the insulation. In a variant,the filling valve is further configured to allow an emptying of theinsulating casing, in particular an emptying into an appropriateinsulation storage box. This can be advantageous in order to change theinsulation or for a repairing of parts of the magnetocaloric device.During an operation of the magnetocaloric device, the filling valve ofthis development is arranged to seal a valve opening of the insulatingcasing, which is provided by the sealing valve. In a preferred variant,the insulating casing can just be filled via the filling valve by usinga respective filling device, which is configured with respect to adesign of the filling valve.

In a further development the insulation is a dry gas. In a variant ofthis development, the dry gas comprises dry air and/or an inert gas suchas nitrogen, helium, neon, argon, krypton, or xenon. Compared toatmospheric air, which has a thermal conductivity of about 0.024 W/(mK)at a temperature of 25° C., argon has a thermal conductivity of about0.016 W/(mK) and krypton of about 0.009 W/(mK) at a temperature of 25°C. Thus, the insulation of this variant can advantageously reduce thethermal conductivity in a surrounding of the magnetocaloric element.

In a further development the insulation comprises a foam, preferably afoam combined with a gas. In a variant of this development, the foam iscombined with solids, as for example milled graphite, which can lead toan advantageously low thermal conductivity of the insulation.

In a further development of the magnetocaloric device a drying agent isprovided in the insulating means, preferably in a carrier that isarranged within the insulating means. The drying agent can additionallysupport a drying of the insulation. Thus the drying agent can reduce thethermal conductivity of the surrounding of the magnetocaloric elementand therefore advantageously improve the efficiency of themagnetocaloric device. The drying agent is preferably formed by an inertsubstance which can be advantageously arranged in the carrier within theinsulation means, in a preferred variant of this development. Thereby,the drying agent that is arranged in the carrier is also in contact withthe insulation in order to support the drying of the insulation.Furthermore, another advantage of the drying agent is that it can incase of leakage and therefore gradual penetration of humidity into theinsulating means a drying of this humidity during operation and afterdays and years of operation without having to perform maintenance on thesystem. Non-limiting examples for the drying agent are silica, silicagel, calcium chloride, metal organic framework materials, a molecularsieve arranged within the insulating means, aluminium oxide, calcium,calcium oxide, calcium hydroxid, calcium sulphate, potassium carbonate,potassium hydroxide, copper sulphate, lithium aluminium hydride, sodiumhydroxid, sodium sulphate, magnesium sulphate, zeolites andsuperabsorbent.

In a further preferred development, the field generator and themagnetocaloric regenerator arrangement are both located in theinsulating means. In a preferred variant of this development, the fieldgenerator comprises a first and a second magnetic body and themagnetocaloric regenerator arrangement is arranged in a magnetic gapformed by the first and second magnetic body. The magnetic gap can besmall in this development, since the magnetic gap is located in theinsulating means so that consequently the insulating means is notlocated in the magnetic gap. A decreasing magnetic gap increases theexternal magnetic field. Therefore, a small magnetic gap can improve theefficiency of the magnetocaloric device and thereby reduces costsarising during an operation of the magnetocaloric device. Particularly,the field generator of this development can be provided in small sizesif the magnetic gap is small. Thereby the material and production costsof the field generator might be reduced. The insulating means of thisdevelopment is preferably formed by the insulating casing. Theinsulating casing allows an insulator to be provided even within a smallmagnetic gap of the magnetocaloric device.

In a further development of the magnetocaloric device all further partsof the magnetocaloric device are located in the insulating means.Further parts can be a motor that rotates the magnetocaloric regeneratorarrangement with respect to the field generator and a crankshaft thatconnects the motor with the magnetocaloric regenerator arrangement orwith the field generator. No further part according to this developmentis a heat exchanger which is connected to the fluid directing system ofthe magnetocaloric device. In order to not disturb a heat exchange ofthe heat exchanger by the insulating material, the heat exchanger isarranged outside of the insulating means. Preferably, the insulatingmeans of the magnetocaloric device of this development is configured toprovide an access for electrical connectors, in order to provide themotor inside the insulating means with electrical power from outside ofthe insulating means.

In a further development the insulating casing is formed as an evacuablevacuum chamber. The thermal conductivity of a gas in the insulatingcasing just depends on, i.e. is proportional to a level of pressure, ifthe mean free path of a particle within the gas is larger than adistance between walls of the insulating casing or the distance betweenother components in the insulating casing preferably such parts that areat different relative temperatures more preferably the distanceespecially the shortest distance between magnetocaloric regenerator andmagnet assembly. Thus, the smaller the magnetic gap, the larger can bethe level of pressure without loosing a proportional dependence betweenthermal conductivity and level of pressure. The mean free path ofparticles in a medium vacuum can be larger than several meters. Thus, byreducing the amount of gas particles in the insulating casing, thethermal conductivity can by decreased, depending on a level of pressure,which is below atmospheric pressure. The mean free path of a particle ina fluid further depends on the mass of the particle. Therefore, it canbe advantageous to use heavy gases as insulation in order to reduce themean free path and therefore reduce the thermal conductivity of theinsulation.

In a preferred development, the magnetocaloric device comprises acrankshaft, which is arranged and configured to move the magnetocaloricregenerator arrangement and the field generator with respect to eachother during an operation of the magnetocaloric device, and wherein theinsulating means allows an access to the crankshaft from an outer sideof the insulating means. The access is preferably provided by a furtheropening of the insulating means, wherein the opening is arranged toleave a shaft gap between insulating means and the crankshaft andwherein a shaft sealing member is arranged to seal the shaft gap. In avariant, the shaft sealing member is formed as a rotational seal or as asealing bearing allowing a rotation of the crankshaft while sealing thegap to the insulating means.

Futhermore, the shaft sealing may be formed in order to thermallydisconnect the shaft from the insulating means. In a variant, this isrealized by using a material with a low thermal conductivity compared tothe materials that the insulating materials and the shaft are made from.This can be ceramic materials, polymeric materials, metals or metalalloys with low thermal conductivity, or a combination thereof.Furthermore, the shape can be such that advantageously little crosssection exists for thermal conduction from the shaft to the insulatingmeans, or a porous or hollow structure can decrease the thermalconnection between the crankshaft and the insulating means.

In a further development, the magnetocaloric device further comprises asupport structure, which is arranged to support the field generator andthe magnetocaloric regenerator arrangement, and wherein the insulatingmeans allows an access to the support structure from the outer side ofthe insulating means to allow an attaching of the magnetocaloric deviceto an external object. The support structure can improve a robustness ofthe magnetocaloric device. The access according to this development canbe provided by screw holes that are provided to attach the supportstructure at the external object via screws. In a variant, the supportstructure is further arranged to provide a constant distance betweeninsulating means and magnetocaloric regenerator arrangement over time.

In a further development, the magnetocaloric device comprises at leastone further magnetocaloric regenerator arrangement comprising a furthermagnetocaloric element, wherein the magnetocaloric element comprisesmagnetocaloric material, and wherein the further magnetocaloricregenerator arrangement is arranged to be exposed to the changingexternal magnetic field, and wherein a further insulating means isprovided such that the further magnetocaloric regenerator arrangement islocated in the insulating means. The further magnetocaloric regeneratorarrangement can increase a total amount of magnetocaloric materialexposed to the external magnetic field and therefore increase theefficiency of the magnetocaloric device. Alternatively, one insulatingmeans can be provided for both the first and any further magnetocaloricregenerator arrangement. This could reduce the costs of such a combinedsystem.

The insulating casing can be made from metal preferably thin metal suchas sheet metal, preferably stainless steel. Alternatively, plasticpreferably engineering plastics such as PVC, ABS, Ultrason, etc. can beused. The insulating casing can furthermore be part of another componentof the magnetocaloric heat pump or of the device, the magnetocaloricheat pump is part of. This may for example be the housing or theinsulation or the support structure of a refrigeration, air-conditioner,or a heat pump in general.

The invention will be apparent and elucidated with reference to theembodiments described hereinafter.

In the following, the drawing shows in:

FIG. 1 a first embodiment of a magnetocaloric device according to theinvention, wherein an insulating casing is located in a magnetic gap ofa field generator;

FIG. 2 a second embodiment of the magnetocaloric device according to theinvention, wherein the field generator and a magnetocaloric regeneratorarrangement are located in the insulating casing, while a motor of themagnetocaloric device is located outside of the insulating casing;

FIG. 3 a third embodiment of the magnetocaloric device according to theinvention, wherein the field generator the magnetocaloric regeneratorarrangement and the motor of the magnetocaloric device are located inthe insulating casing.

FIG. 1 shows a first embodiment of a magnetocaloric device 100 accordingto the invention, wherein an insulating means 105 formed by aninsulating casing 110 is located in a magnetic gap 125 of a fieldgenerator 120.

The magnetocaloric device 100 of this first embodiment is amagnetocaloric heat pump, which comprises the field generator 120,comprising the magnetic gap 125 between a first magnet assembly 126 anda second magnet assembly 128, and a magnetocaloric regeneratorarrangement 130, arranged in the magnetic gap 125. The magnetocaloricregenerator arrangement 130 comprises a plurality of magnetocaloricelements 132, wherein each of the magnetocaloric elements 132 comprisesmagnetocaloric material 135, and wherein the magnetocaloric regeneratorarrangement 130 is arranged to be exposed to a periodically changingexternal magnetic field 122, which is provided by the field generator120.

The magnetocaloric device 100 further comprises a fluid directing system140, comprising a first 141, a second 142, a third 143 and a fourth 144channel, arranged to direct a cold fluid through the first channel 141to the magnetocaloric regenerator arrangement 130 and to direct the coldfluid through the second channel 142 away from the magnetocaloricregenerator arrangement 130, and to direct a hot fluid through the thirdchannel 143 to the magnetocaloric regenerator arrangement 130 and todirect the hot fluid through the fourth channel 144 away from themagnetocaloric regenerator arrangement 130. The fluid is therebydirected according to magnetization and demagnetization phases of aprocess cycle of the magnetcaloric heat pump 100, wherein the processcycle is well known by prior art. The cold fluid, which is directedthrough the second channel 142 away from the magnetocaloric regeneratorarrangement 130 is directed to a first heat exchanger 146 before it isagain directed through the first channel 141 to the magnetocaloricregenerator arrangement 130. The hot fluid, which is directed throughthe fourth channel 144 away from the magnetocaloric regeneratorarrangement 130 is directed via a pump 147 to a second heat exchanger148 before it is again directed through the third channel 143 to themagnetocaloric regenerator arrangement 130.

According to the invention, the magnetocaloric device 100 furthercomprises the insulating casing 110, wherein the magnetocaloricregenerator arrangement 130 is located in the insulating casing 110 andthe insulating casing 110 is arranged such that the magnetocaloricregenerator arrangement 130 is hermetically surrounded by the insulatingcasing 110 with a flow-through 150 for a passing of the fluid throughthe first 141, second 142, third 143 and fourth 144 channel. Theflow-trough 150 is arranged to leave a gap between insulating casing 110and the channels 141, 142, 143, 144 and a flow sealing member 155 isarranged to seal the gap. Furthermore, the insulating casing 110 isfilled with an insulation 160 that has a lower thermal conductivity thanatmospheric air.

In the depicted embodiment, the insulation 160 is dry air and a dryingagent 165 is additionally provided in a carrier 168 that is arrangedwithin the insulating casing 110. The drying agent 165 additionallyreduces a humidity of the dry air, in order to reduce the thermalconductivity of the insulation 160. In an embodiment not shown, theinsulating casing is formed as an evacuable vacuum chamber.

The insulating casing 110 is arranged in the magnetic gap 125 of thefield generator 120. A motor 170 of the magnetocaloric device 100 isconnected to a power supply (not shown) via electrical connectors 175and is arranged to rotate the first and second magnet assembly 126, 128of the field generator 120 during an operation of the magnetocaloricdevice by rotating a crankshaft 180 that is attached to the first andsecond magnet assembly 126, 128. The insulating casing 110 allows anaccess to the crankshaft 180 from an outer side of the insulating casing110. The access is provided by a first and a second opening 182, 184 ofthe insulating casing 130, wherein the first and second opening 182, 184is arranged to leave a shaft gap between insulating casing 110 and thecrankshaft 180 and wherein a respective shaft sealing member 185 isarranged to seal the respective shaft gap. The shaft sealing member 185is formed as a rotational seal allowing a rotation of the crankshaft 180while sealing the shaft gap to the insulating casing 110. In anembodiment not shown, the sealing member is formed as a sealing bearing.

In further preferred embodiments, any kind of insulation means isarranged in the magnetic gap instead of an insulating casing. Inparticular, an insulating coating is provided in a preferred embodimentnot shown, wherein the insulating coating is completely in contact withthe magnetocaloric regenerator arrangement. The insulating coating canbe for instance a foam, a varnish, a paint or a foil.

In a further embodiment not shown, the crankshaft is arranged to rotatethe magnetocaloric regenerator arrangement while the field generator isfixed. The channels of the fluid directing system of this furtherembodiment are arranged in the crankshaft and connected to themagnetocaloric regenerator arrangement via rotary valves.

The insulating casing 110 further comprises a filling valve 188 arrangedat the insulating casing 110 and configured to allow a filling of theinsulating casing 110 with the insulation 160. The filling valve 188 isfurther configured to allow an emptying of the insulating casing 110, inparticular an emptying into an appropriate insulation storage box.

The magnetocaloric device 100 according to the embodiment shown in FIG.1 further comprises a support structure 190, which is arranged tosupport the field generator 120 and the magnetocaloric regeneratorarrangement 130, and wherein the insulating casing 110 allows an accessto the support structure 190 from the outer side of the insulatingcasing 110 to allow an attaching of the magnetocaloric device 100 to anexternal object 195.

In an embodiment not shown, the magnetocaloric device comprises at leastone further magnetocaloric regenerator arrangement comprising a furtherplurality of magnetocaloric elements, wherein each of the magnetocaloricelements comprises magnetocaloric material, and wherein the furthermagnetocaloric regenerator arrangement is arranged to be exposed to theperiodically changing external magnetic field, and wherein a furtherinsulating casing is provided such that the further magnetocaloricregenerator arrangement is located in the insulating casing. In thisembodiment, the magnetocaloric regenerator arrangement and the furthermagnetocaloric regenerator arrangement are both arranged in the magneticgap of the field generator. In a further embodiment not shown, themagnetocaloric device is provided such that the first magnetic assembly,the magnetocaloric regenerator arrangement, the second magneticassembly, the further magnetocaloric regenerator arrangement and a thirdmagnetic assembly are arranged in this order along the crankshaft. In analternative embodiment not shown, an insulating casing is provided suchthat the magnetocaloric regenerator and the further magnetocaloricregenerator are located in the insulating casing.

FIG. 2 shows a second embodiment of the magnetocaloric device 200according to the invention, wherein the field generator 120 and themagnetocaloric regenerator arrangement 130 are located in the insulatingcasing 210, while the motor 170 of the magnetocaloric device 200 islocated outside of the insulating casing 210.

The magnetocaloric device 200 is arranged as the magnetocaloric device100 shown in FIG. 1, the only difference is that in addition to themagnetocaloric regenerator arrangement 130, the field generator 120 isalso located in the insulating 210 casing. As a consequence, the firstand second opening 182, 184 of the insulating casing 210, which formsthe insulating means 205 are not provided in the magnetic gap 125, butbetween field generator 120 and motor 170, and between field generator120 and a bearing 220 of the crankshaft 180.

For embodiments, wherein the magnetocaloric regenerator arrangement andthe field generator are located inside the insulating means, the use ofan insulating casing as insulating means, as shown in FIG. 2, ispreferred. However, using an insulating coating, such as a foam, is alsopossible and within the scope of the present invention. The insulatingcasing is filled with atmospheric air in further variants of theembodiment shown in FIG. 2.

The support structure 190 is arranged as shown in FIG. 1 to support thefield generator 120 and the magnetocaloric regenerator arrangement 130,but not illustrated in FIG. 2 for reasons of clarity.

FIG. 3 shows a third embodiment of the magnetocaloric device 300according to the invention, wherein the field generator 120 themagnetocaloric regenerator arrangement 130 and the motor 170 of themagnetocaloric device 300 are located in the insulating casing 310,which forms the insulating means 305.

In contrast to the magnetocaloric device 100 shown in FIG. 1, the fieldgenerator 120 and the motor 170 are also located in the insulatingcasing 310. Furthermore, the crankshaft 180 is completely located in theinsulating casing 310 so that there is not a first and a second opening182, 184, but a bearing 320 of the crankshaft 180 within the insulatingcasing 310. This bearing may or may not be connected to or supported bythe insulating casing. To enable an electrical connection, a connectionopening 330 is provided in the insulating casing 310 for the electricalconnectors 175. Thereby the electrical connectors enable an electricalpower supply of the motor 170 from outside of the insulating casing 310.The opening 330 comprises a connector gap between the electricalconnectors 175 and the insulating casing 310, wherein a connectorsealing member is arranged to seal the gap.

Furthermore, the support structure 340 is arranged in the insulatingcasing 310 in contrast to the support structure 190, illustrated inFIG. 1. Alternatively, the support structure and the insulating casingmay be one component serving both functions or they may be attached orintegrated into each other. Therefore, the insulating casing 310 formsan outer surface of the magnetocaloric device 300 and can be attached tothe external object 195, in order to provide the magnetocaloric device300 in a fixed position.

In an embodiment not shown, the motor is further insulated by anadditional insulating casing, which guides heat from the motor to anoutside of the insulating casing, preferably with cooling fins thatconnect the additional insulating casing with the insulating casing.Thus, the device of this embodiment advantageously reduces a heatproduction inside the insulating casing, compared to the embodimentshown in FIG. 3.

List of Reference Signs:

100 magnetocaloric device

105 insulating means

110 insulating casing

120 field generator

122 external magnetic field

125 magnetic gap

126 first magnet assembly

128 second magnet assembly

130 magnetocaloric regenerator arrangement

132 magnetocaloric element

135 magnetocaloric material

140 fluid directing system

141 first channel

142 second channel

143 third channel

144 fourth channel

146 first heat exchanger

147 pump

148 second heat exchanger

150 flow-trough

155 flow sealing member

160 insulation

165 drying agent

168 carrier

170 motor

175 electrical connector

180 crankshaft

182 first opening

184 second opening

185 shaft sealing member

188 filling valve

190 support structure

195 external object

200 second embodiment of the magnetocaloric device

205 insulating means of the second embodiment

210 insulating casing of the second embodiment

220 bearing of the crankshaft

300 third embodiment of the magnetocaloric device

305 insulating means of the third embodiment

310 insulating casing of the third embodiment

320 bearing of the crankshaft of the third embodiment

330 connection opening

340 support structure of the third embodiment

1. A magnetocaloric device, comprising: a field generator, arranged toprovide a changing external magnetic field, a magnetocaloric regeneratorarrangement, comprising a magnetocaloric element, wherein themagnetocaloric element comprises magnetocaloric material, and whereinthe magnetocaloric regenerator arrangement is arranged to be exposed tothe changing external magnetic field of the field generator, wherein inthat the magnetocaloric device further comprises: an insulator, whereinthe insulator is arranged such that the magnetocaloric regeneratorarrangement is hermetically surrounded by the insulator.
 2. Themagnetocaloric device according to claim 1, further comprising: a fluiddirecting system, comprising at least a first and a second channel,arranged to direct a fluid through the first channel to themagnetocaloric regenerator arrangement and to direct the fluid throughthe second channel away from the magnetocaloric regenerator arrangement,and wherein the insulator further comprise a flow-through for a passingof the fluid through the at least first and second channel.
 3. Themagnetocaloric device according to claim 1, wherein the insulator is aninsulating casing, which is at least partly not in contact with themagnetocaloric regenerator arrangement, and wherein the insulationcasing is filled or adapted to be filled with an insulation.
 4. Themagnetocaloric device according to claim 1, wherein the insulator is aninsulating coating, which is completely in contact with themagnetocaloric regenerator arrangement.
 5. The magnetocaloric deviceaccording to claim 3, wherein the insulation has a lower thermalconductivity than atmospheric air.
 6. The magnetocaloric deviceaccording to claim 3, wherein the flow-trough is arranged to leave a gapbetween insulating casing and the at least first and second channel andwherein a sealing member is arranged to seal the gap.
 7. Themagnetocaloric device according to claim 3, further comprising: afilling valve arranged at the insulating casing and configured to allowa filling of the insulating casing with the insulation.
 8. Themagnetocaloric device according to claim 3, wherein the insulation is adry gas.
 9. The magnetocaloric device according to claim 8, wherein thedry gas comprises dry air and/or an inert gas, nitrogen, helium, neon,argon, krypton or xenon.
 10. The magnetocaloric device according toclaim 1, wherein a drying agent is provided in the insulator.
 11. Themagnetocaloric device according to claim 1, wherein the field generatorand the magnetocaloric regenerator arrangement are both located in theinsulator.
 12. The magnetocaloric device according to claim 11, whereinall further parts of the magnetocaloric device are located in theinsulator.
 13. The magnetocaloric device according to claim 11, whereinthe insulating casing is formed as an evacuable vacuum chamber.
 14. Themagnetocaloric device according to claim 1, wherein the magnetocaloricdevice comprises a crankshaft, which is arranged and configured to movethe magnetocaloric regenerator arrangement and the field generator withrespect to each other during an operation of the magnetocaloric device,and wherein the insulator allows an access to the crankshaft from anouter side of the insulating means.
 15. The magnetocaloric deviceaccording to claim 14, wherein the crankshaft is arranged to leave ashaft gap between insulating casing and the crankshaft and wherein ashaft sealing member is arranged to seal the shaft gap.
 16. Themagnetocaloric device according to claim 1, further comprising: asupport structure, which is arranged to support the field generator andthe magnetocaloric regenerator arrangement, and wherein the insulatorallows an access to the support structure from the outer side of theinsulator to allow an attaching of the magnetocaloric device to anexternal object.
 17. The magnetocaloric device according to claim,wherein the magnetocaloric device comprises at least one furthermagnetocaloric regenerator arrangement comprising a furthermagnetocaloric element, wherein the magnetocaloric element comprisesmagnetocaloric material, and wherein the further magnetocaloricregenerator arrangement is arranged to be exposed to the changingexternal magnetic field, and wherein a further insulator is providedsuch that the further magnetocaloric regenerator arrangement is locatedin the further insulator.